The invention applies to the field of data transmission based on a unidirectional broadcast system and more specifically refers to an adapter which implements the receiver function of the system.
U.S. Pat. No. 4,829,569 discloses a subscription television system in which individual decoders are enabled to receive individually addressed messages. However, the cited prior art patent does not teach how to organize for a selective transmission of data or how to selectively receive such data. According to the prior art, individual decoders in a subscription television system can be addressed for transmission of either billing information or individual messages; this suggests only a distinction between a transmission directed to a single addressee and a broadcasting transmission. The same scheme may be applied to non subscription television, substituting the decoders With a special-purpose device.